OCR Chemistry A F322 Chains, Energy and Resources Wed 23 May 2012

Why are people struggling on the last question!? I found that one of the easier ones!! :O I found the enthalpy questions tricky. But I got an answer, just didn't know whether I got the positive or negative sign the right way around :frown:

(

Reply 1581

godknows

I got 1-iodo-2methylpropane for B .. 2-mehtylpropanoic acid for D... and 2-methlypropanol for C :s

Reply 1582

Joseppea

2

Original post by Namod

there was a very broad O-H peak due to carboxylic acid

I read on mark scheme based on a spectrum identical to that, that it didn't classify as a carboxylic acid because it wasn't curved enough, and the peak was due to C-H. Otherwise, I would've put carboxylic acid for sure! :tongue:

Last time I listen to any of those mark schemes. :mad:

Oh well, my reasoning from that was valid, so I shouldn't lose too many marks. >_<

Reply 1583

med123

for the margarine question, there was a similar in jan 2011 7d, answers were react with hydrogen and use a nickel catalysts

so you had to say react unsat compounds in plant oils with hydrogne n use a nickel cataylsts

Reply 1584

godknows

Original post by Nick_

i put infrared spectrometry instead of infrared spectroscopy, damn

I put infrared radiation in a hurry.. can it get any worse :frown:

Reply 1585

StephenDudge

Original post by FailedMyExams

Can somebody talk me through the Percentage Yield question please?

I got 184 and knew that wasn't right so I flipped the equation and got 58.6 or something.

Annoys me because I used my intuition to predict that it wouldn't be the first answer, but if I left it as I did I probably would've got 2/3 marks instead of 1/3.

You calculated the moles of each one, bearing in mind the ratio. And sub over eachother, was like 90odd percent?

Reply 1586

pwcroberts

2

The last one the spectrum was of a c acid definitely and it was methyl propanoic acid, alcohol was methyl propan-1-ol and halogenolakane was 1-iodomethylpropane

Reply 1587

Little Wing

9

Original post by FailedMyExams

Can somebody talk me through the Percentage Yield question please?

I got 184 and knew that wasn't right so I flipped the equation and got 58.6 or something.

Annoys me because I used my intuition to predict that it wouldn't be the first answer, but if I left it as I did I probably would've got 2/3 marks instead of 1/3.

You had 200x10^6g of methane. Find the moles of that.
You had 68.4x10^6 of 3H2, so divide 68.4tonnes by 3 then find the moles.
(Moles of methane/moles of hydrogen) x100

Reply 1588

PrettyLittleLiars

Original post by Dizzie31

Can someone also explain how you got the D to be butanoic acid?
i got methanoic and im baffled about that.

i gt methanoic acid too

Reply 1589

louci

7

ddid anyone get +82 kjmol-1 for the delta H reaction thing ??

Reply 1590

scorpio22

12

Original post by aallaa

what people got for %yield? and cracking question. Margarine was easy nickel catalyst 150 C and hydrogen from unsaturated making saturated margerine

i drew out the equation lool...
i coouldnt explain it in worlds...thankgoodness its chemistry and you can do equations

Reply 1591

duharvalgt

7

Original post by IAmMclovin

It was 1-iodomethylpropane, and methylpropan-1-ol, how else could methylpropene have been formed by the dehydration reaction?

I wrote , iodomethylpropane and methylpropanol is that the same molecule or will I not get the marks?

Reply 1592

Joseppea

2

Original post by anuradha_d

THATS EXACTLY WHAT I THOUGHT! thats my answer... but there was no sensible structure for it, because C was methylpentanol...
I just didnt draw a diagram for it :/

Oh good, I'm glad I wasn't the only one who did it :P

On all the google images of carboxylic acid IR spectra, there is a slight smooth curve to them, there wasn't one in this though. :s-smilie:

Had major issues about converting C to methylpentene because of that. Not clear either way!

Reply 1593

godknows

i got 237% or something for percentage yield :'(

Reply 1594

RuksanaBegum

Work out moles for reactant, multiply by 3 (1:3 ratio)
Work out moles of H2,

H2 moles / Reactant moles x 100
92.1% or something

This was posted from The Student Room's iPhone/iPad App

Reply 1595

poyyo

6

i thought i did good but now i feel like i made way too many silly mistakes to get an A :frown:

Reply 1596

Issy123

11

How do you all think the grade boundaries will be? i think they'll be low or normal depending on how many people found it difficult! I don't think they'll be high though and definitely not higher than Jan 2012!

Reply 1597

RuksanaBegum

Original post by godknows

i got 237% or something for percentage yield :'(

Had to divide by 3, you missed out the ratios..

This was posted from The Student Room's iPhone/iPad App

Reply 1598

YB101

17

Original post by med123

for the margarine question, there was a similar in jan 2011 7d, answers were react with hydrogen and use a nickel catalysts

so you had to say react unsat compounds in plant oils with hydrogne n use a nickel cataylsts

I just put the equation and the catalyst used

Reply 1599

canabel

1

Original post by YB101

I could have SWORN the question said that the product was split into 2 portions, one reacting with something (i can't remember) to form methylpropane and the other reacting with the [O] therefore wouldn't that HAVE to make Butanoic acid seeing as C was CH3CH2CH2OH?

i think that is where the problem lies. The paper did say it was split into two and each portion reacted with different things

i put butane instead of propane -o-
will they give no marks-o-

OCR Chemistry A F322 Chains, Energy and Resources Wed 23 May 2012

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